Initial commit: JMon cross-platform monitoring system

- gRPC client-server metrics collection
- PeriodicTimer-based 5-second sampling
- Delta encoding with configurable thresholds
- Queue/retry mechanism for resilience
- ProcessId tracking for duplicate detection
- Server-side state reconstruction
- Native AOT compilation support
- Docker/Podman containerization
- PostgreSQL + TimescaleDB persistence layer

JMonAgent/Program.cs

@@ -0,0 +1,8 @@
+using JMonAgent;
+
+var builder = Host.CreateApplicationBuilder(args);
+builder.Services.AddSingleton<MetricsQueue>();
+builder.Services.AddHostedService<Worker>();
+
+var host = builder.Build();
+host.Run();